Electrical discharge device



Patented June 13,- 1944 ELECTRICAL DISCHARGE DEVICE Alexander C. Wall, Indianapolis, Ind., assignor to General Electric Company, a corporation of New York ,Application May 2, 1942, Serial No. 441,419

5 claims. (cl. 31a- 326) My invention relates to'spark plugs.

An object of my invention is to provide an improved spark plug having a construction which minimizes the possibility of flash-over within the plug by substantially eliminating gas electrical discharge paths between the distribution lead and y the shell of the plug.

Further objects and advantages of my inveition vwill become apparent and my invention will be better understood from the following description referring to'the accompanying drawing, and` the features of novelty which characterize my invention will be pointed out with particularity in the claims annexed to and forming part of this specification.

'I'he drawing is an elevational view, partly in` section, .of a spark plug and a distribution lead illustrating an embodiment of my invention.

Referring to the drawing, I have shown a spark plug provided with an outer metallic sleeve or barrel I threaded at one end II for engagement with a complementary threaded opening in an engine block and having an enlarged portion I2 adapted to be engaged by a wrench or similar tool. Grounding electrodes I3 are secured to the shell III adjacent the lower threaded end II and a central or discharge electrode I4 is supported within the spark plug by a ceramic insulating core I5 of porcelain or similar material. The discharge electrode I4 is formed with a lower flange It which engages a complementary shoul der I1 on the insulating'core I 5 and is provided with a turned-over contact head portion I8 which secures a cap I9 in position over a central opening in the insulating core I5. This central opening 20 in the core I5 between the electrode ilange I6 and the cap I8 is lled with a body of compressed or compacted powder. The core I! is held in position in the shell I0 by engagement adjacent its lower end with a gasket 2| seated on a shoulder 22' formed on the shell I0 `and by engagement at the opposite end thereof with a turned-over end 23 of .the shell I0.

sition on the spark plug by a terminal elbow 2l which issecured to the head of the spark plug shell III by a nut 28 which threadedly engages a threaded upper end portion 29 of the plug shellv Il and is provided with an annular ilange 30 exelbow 2l. Thecentral spark plug electrode I4 is electrically connected through a coil spring 33 which is connected to the lead 24 through a terminal washer 32.

Under certain atmospheric conditions, such as relatively low pressure, there is a tendency for the voltage to discharge from the lead to the grounded plug shell through any gas discharge path. In order to eliminate corona and arc-over discharges, the flange 3| of the terminal elbow 2l is arranged in engagement with a relatively nondeformable cap element 34 of insulating material arranged in engagement with the upper end of a heat resistant bushing 35 formed of deformable resilient insulating material, such as the composition produced by a mixture of polystyrene and polyisobutylene or Oppanol as described in British Patent No. 513,630 (1939). This bushing 35 is arranged about the -lead 24 4and its insulation 25 within the shell I0 between the electrical connection of the lead 24 to the electrode I4 and the upper end of the shell IIL When the nut 28 is secured in position, it draws the ilange 3| of the terminal elbow 2l downwardly into engagement with the upper end of the cap 34 which compresses and deforrns the bushing 35 and substantially circumferentially illls a longitudinal portionof the space about the lead within the shell 4between the terminal washer -32 and the upper end of the shell, thereby eliminating free open gas electrical discharge paths between the -shell and the lead, thus effectively sealing the space between the shell and the terminal connection 32. With this arrangement any decrease in air pressure around the plug will tendto cause the air trapped within the plug tending over a complementary ilange 3l on the 55 by the bushing 3B to exert pressure on the bushing and. to compress it into more intimate contact with the adjacent surfaces to provide a better seal and to assure against any air discharge paths.

While I have illustrated and described a particular embodiment of my invention, modifications thereof will occur to those skilled in the art. I desire it to be understood, therefore, that ny invention "is not to be limited to the particular arrangements disclosed, and Iintend in the appended'claims to cover all modilcationswhich do not depart from` the Spirit and scope of my invention.

What I claim as `new and desire to secure by Letters Patent of the United States, is:

1v. A- spark plug including a shell having a grounding electrode, a discharge electrode arranged within said shell, an insulating element arranged between a part "of said discharge electrode and said shelll a distribution lead of conductive material electrically connected to said discharge electrode within said shell, and means including a heat resistant bushing of deformable insulating material arranged between said shell and said electrical connection of said lead to said discharge electrode arranged in deformed position for substantiallv iilling a portion of the space between said lead connection and said insulating element and for eliminating free openv gas electrical discharge paths between said connection and said shell.

2. A spark'plug including a shell having a grounding electrode, a discharge electrode arranged within said-shell, an insulating 'element arranged between a part of vsaid discharge electrode and said shell, a distribution lead of conductive material electrically connected to said 'discharge electrode within said shell, a heat resistant bushing of deformable insulating material arranged between said shelland said electrical connection of .said lead to said discharge electrode, and means including a relatively non deformableA element arranged in engagement with said deformable bushing deiorming' said bushing for substantially lling a portion of the space between said lead connection and said insulating element and for eliminating free open gas electrical discharge paths between said connection and said shell.v

3. A spark plug including a shell having a grounding electrode, aV discharge electrode arranged within said shell, an insulating elementV arranged between a part of said discharge e1ectrede-and said shell, a distribution lead ot conductive material electrically connected' to said discharge electrode within said shell, 'a heat rcsistant bushing of deformable insulating material arranged within said insulatingelementabout a portion of said lead between said connection of said lead to said electrode and the end of said ment arranged in engagement with said deformv, able bushing iordeforming said bushing and substantially circumferentiallly illling a longitudinal portion oi the space about said lead within said insulating element eliminating free open gas electrical discharge paths between said shell and said lead. 4

- 4. A spark plug including ashell having a grounding electrode, a discharge electrode arranged within said shell, an insulating -element l arranged between a part oi said discharge electrede and said shell, a distribution leadv of conductive materialv electrically connected to said discharge electrode within said shell, insulation arranged about said lead and extending within v said shell about a portion of said lead, a heat resistant bushing'of deformable resilient insulating material arranged within saidshell about a portionof said1 lead insulation, and means including a relatively non-deformablev cap arranged in engagement with said deformable bushing for dea forming said bushing and substantially circumg ferenti'ally iilling a longitudinal portion of saidA space about said lead insulation within said insulating element eliminating free open gas electrical discharge paths between said shell and said lead.

5. A spark plug including a shell having a grounding electrode, a-discharge electrode arranged within said shell, means including an insulating element arranged between a part of saiddischarge electrode and said shell forsupporting said electrode in said shell, a distribution lead of conductivematerial electrically connected to said discharge electrode within said shell, insulation insulating element away from said electrode, and means including a relatively non-deformable elel arranged about said lead and extending within said shell about a portion of said lead, a heat -1"e' sstant bushing 'of deformable resilient insulating Ymaterial arranged between said shell and said electrical connection of said lead to said dischargel electrode, and means including a relativelynon-deformable element arrangedv in engagement with said deformable bushing deform-v, ing said bushing for substantially lling a portion of the space between said lead connection and said insulating element and for eliminating-tree open gas electrical` discharge paths between said shell and said connection.

c. WALL'. 

